This project seeks to answer the question of whether Magnesium administered during Cardiopulmonary Bypass Surgery provides protection for the brain. In the study, heart surgery patients will be randomized to receive Mg or placebo after anesthesia induction. Plasma levels of Mg will be drawn in the perioperative period. Apolipoprotein Ee-4 alleles will be determined. Neurologic evaluations will be done preoperatively, on day 3-5 postoperatively, at 6 weeks and 1 years after surgery. We will study 200 patients over 2 years and determine whether Magnesium has neuroprotective benefit.